The history of sexually transmitted diseases is thought to date back to earliest times, and many ancient texts describe conditions that may be those of syphilis and gonorrhea, which at one time were thought to be the same disease. A main figure in the research in this area was Albert Ludwig Sigesmund Neisser, who discovered the gonococcus in 1879 and later produced the most comprehensive account of experimental syphilis ever published. This article provides a brief biography of Albert Neisser, focusing on his discoveries in the area of infectious diseases, the so-called Neisser-Hansen controversy, and the situation leading to changes in defining bioethics.